The present invention relates to a folded and brazed tube for a heat exchanger such as a radiator for cooling a motor-vehicle engine, for example.
More precisely, the invention relates to such a tube consisting of a metal strip having an outer face and an inner face, the outer face being covered with a plating of brazing alloy, the metal strip being folded by passage through a series of successive rollers and including at least one folded border having a sheared edge bearing on an inner face of the metal strip.
In a tube of this type, the sheared edge of the metal strip originates from the cutting-cut of a foil of greater length, and it does not include any plating of brazing alloy. Moreover, the inner face of the metal strip, which is generally covered with an anti-corrosion layer, is not covered with brazing alloy either joining by brazing of the inner face with the border is very problematic.
It might be thought to resolve this problem by depositing some brazing alloy on the sheared edge of the metal strips. However, such an operation would be intricate to carry out and would be expensive.
The precise object of the present invention is a tube for a heal exchanger in embodiments of which a joint by good-quality brazing between the border and the inner races of the tube can easily be obtained.
This object may be achieved, in accordance with the invention, by the fact that the sheared edge of the metal strip is covered with a layer of brazing alloy.
The present of this quantity of brazing alloy allows a quality joint between the two pieces, namely a joint which is both leaktight and mechanically tough.
In one preferred embodiment of the invention, the layer of brazing alloy is pushed back mechanically from the outer face towards the sheared edge.
Particularly advantageously, the layer of brazing alloy is pushed back by the abovementioned rollers.
The invention also relates to a method of manufacturing a tube by folding of a metal strip including a plating of brazing alloy on an outer face. According to this method, the metal strip is made to pass between a series of rollers which are shaped to push back the layer of brazing alloy from the outer face towards the sheared edge.
Advantageously, each roller includes a surface which exhibits an angle of inclination with respect to its rotational axis, the angles of inclination of the successive rollers continually increasing.
Finally, a heat exchanger according to the invention, especially for a motor vehicle, consists of a bank of tubes alternating with corrugated spacers, the sheared edge of the borders of the tubes being covered with a layer of brazing alloy. This layer has preferably been pushed back by rollers from the outer face towards the sheared edge.
Other characteristics and advantages of the present invention will emerge further upon reading the description which follows of embodiment examples given as an illustration by reference to the attached figures.